<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="text" value="abc">
<input type="button" value="按钮" onclick="fn()">
<div></div>
<!--引入jq框架-->
<script src="https://cdn.staticfile.org/jquery/2.1.1/jquery.min.js"></script>
<script>
    function fn() {
        //取出文本框的值
       //alert($("input:first").val());

       //修改文本框的值
        //$("input:first").val("啦啦啦");
        //取出文本框的值给到div
        $("div").text($("input:first").val());
    }
</script>
</body>
</html>